The goal of this multi-investigator project is to develop an animal model of HIV neuropathology that can be used to assess: 1) cognitive function, 2) neuronal and non-neuronal degeneration in the prefrontal cortex and 3) electrophysiological properties of cells and circuits in prefrontal cortical networks. With the advent of improved combination antiretroviral therapy, HIV infection has been transformed from a fatal illness to a chronic manageable condition. This trend has resulted in an increasingly large population of aging individuals with prolonged exposure to HIV neurotoxins and to HIV therapeutic interventions. While there are excellent tissue culture models for studying the impact of HIV or HIV therapy on cellular processes, the options for in vivo investigation of the effects o HIV infection or chronic antiretroviral therapy are more limited, particularly as they relate to th aging brain. The ideal model for investigating such issues would provide the opportunity to examine and correlate cognitive performance with electrophysiological indices of neural function and neuropathology across the aging continuum with respect to onset of the HIV infection and progression of ensuing disease processes. The work outlined in this proposal will focus on CNS exposure to the HIV envelope protein gp120 in adult and aged rats and its impact on 1) performance of two prefrontal cortex-dependent behavioral tasks, 2) neuronal excitability and synaptic transmission in the prefrontal cortical circuitry and 3) the degree of neurotoxic insult t neuronal and non-neuronal cells in the prefrontal cortex. The most important aspect of this investigation is the development of an animal model that will have advantages for numerous additional in vivo studies focusing on the broad array of potential agents and mechanisms associated with HIV infection and its treatment, the time course of these events, and their impact on the aging brain. In particular this model will facilitate the identification and development of new targets and new compounds for therapeutic interventions in adult and aging HIV/AIDS patients. Across all inquiries, the model will validate the findings of in vitro tissue culture studies and their relevance to normative functions in the intact central nervous system.